Five men wearing balaclavas and armed with kives and a gun forced their way into the home in Plaistow just before 3am on Friday.
A 23-year-old man has been arrested on suspicion of attempted murder. Detectives believe the attackers were looking for a member of a gang and attacked him by mistake.
This morning a Scotland Yard spokesperson said: 'The person who may have been involved in a gang was staying at the address and they may have been the target, but the boy who was attacked had no criminal background.'
The neighbour, who did not want to be identified, said: 'It was quiet on Thursday night, all I heard was the banging as they booted the door in and then another bang, but it didn't sound like a gun shot to me at the time.'
The neighbour said they could see a woman banging on other neighbours' doors and screaing 'please help my son' when they looked into the street.
Detectives believe the attackers were looking for a member of a gang and attacked the teenager by mistake
'I ran down and we went into their house, he was lying on the landing floor and there was a lot of blood on the carpet and on the wall.
'His mum and sister had wrapped his leg up to stop the bleeding, the people trying to help him were panicking so I took over.
'I kept him talking, he was going into shock and was really confused. He was bleeding a lot from his lower right calf and his sister was begging the paramedics to come quicker over the phone.
Paramedics arrived at the scene before taking the teenager, the son of a biochemist, to hospital.
The neighbour said: 'It felt like ages before the paramedics arrived, I was so scared that there was a 15-year-old boy who was bleeding out.
'Thank God he's ok, he seemed like a regular lad from a regular family, it's so shocking.
'They were just a normal, nice family, who kept themselves to themselves. I don't know why they would attack him, there's been no-one like that hanging around their house.'
A police spokesman said: ‘Police patrols have been increased in the area in order to provide reassurance to the local community.’
The Trident Gang Crime Command are investigating the incident.
Culled from Daily Mail